Technical Field
This disclosure is directed to memory subsystems, and more particularly, calibration of signals conveyed in memory subsystems.
Description of the Related Art
Eye diagrams, are graphic illustrations that illustrate times and amplitudes at which a digital signal can be sampled at its correct value. In various types of systems that include data transmissions, sampling of signals (based on a clock signal) near a center of an eye, in terms of time, may be desirable. This may provide a signal with a sufficient amount of both setup and hold time, while also rendering it less susceptible to noise. In sampling a signal, a threshold voltage is used to determine whether the signal is interpreted as a logic 0 or a logic 1.
In memory systems, calibrations may be performed to determine the points at which signals are sampled within the eye opening. Calibrations may be performed to determine both the point in time at which signals are sampled, as well as to determine the threshold voltage for distinguishing between logic 0's and logic 1's. The calibration to determine the point in time at which signals are sampled may be referred to as a horizontal calibration. The calibration to determine the threshold voltage may be referred as a vertical calibration. In many memory systems, these calibrations are performed at regular intervals, and typically, in conjunction with one another.